Post-Combustion Capture – Solid Sorbents

Post combustion capture refers to separation of CO2 from the effluent stream of combustion of some hydrocarbons. For carbon capture and storage (CCS), estimates are that 80% of the cost is for the capture stage, and this is owed primarily to large energy costs to regenerate and recycle sorbent systems. Traditional methods use amine scrubbing that require large amounts of energy to regenerate the system as, beyond releasing CO2, heating a large volume of water -70%- is needed. A solid sorbent system offers potentially much lower costs than traditional technology for post-combustion flue gas capture. Scaling this technology to the volumes in flue gas is a challenge but one that is minimized proportionally by having sorbents that trap greater amounts of CO2. The pathway below describes how the different teams will engage in research and the added value of the training experience for HQP.

Materials Development: The Shimizu and Sayari groups make new solid sorbents. The Shimizu group makes Metal organic frameworks (MOFs) that are a newer class of porous solid sorbents that haves shown record capacities for CO2. The greatest pitfalls of MOFs have been cost and low stability to water, however, both of these issues can and have been addressed by the Shimizu group and others. The Shimizu group has a MOF, known as CALF-20 (PCT patent filed), that is made from mass produced starting materials, is highly water stable and has outstanding CO2 capacity at low CO2 pressure. A new spin-off company (Bow Valley Innovations) has resulted from this work. The Woo group has developed algorithms for predicting new solid sorbents computationally but also for predicting the CO2 capacity for flue gas capture and have predicted new materials with more than double the capacity of the best solid sorbents known. Sayari studies amine-modified silica but his materials would follow a parallel development.

Process Engineering: Solid sorbents are made as powders. The best solid sorbent based on CO2 capacity and selectivity alone, if simply packed into a separation bed, would give massive back pressures and localized heating problems that would make functional CO2 separation impossible. A powder must be made into a structured form to enable efficient mass and heat transfer. Minimally, granularization of the powder could be carried out but also more elaborate options exist such as formation of laminates (2-D) and 3-D structured macroscopic particles. Collaborator Akhtar has expertise and instrumentation to carry out such studies (author of 2014 review). Gas separation studies (competitive breakthrough experiments) will be carried out on structured sorbents and iteratively used to optimize materials development. The durability of structured sorbents will also be assessed.

System Engineering: Raw outputs from process engineering will be used to model (Rajendran) the optimal functioning of a CO2 capture system factoring in the energy needed to regenerate the separation bed. These data will enable estimation of the optimal material and structuring needed to practically capture CO2 from a 50MW coal fired power plant. The kinetics of capture and release are as important as the capacity and are factors rooted in both the chemistry and engineering of the solid. Gates has a steam chamber being retrofitted to allow measurement of CO2 capture by solids. No individual group mentioned in Theme A has the expertise or infrastructure to carry out all the important steps in the development of a carbon capture material. As mentioned, all HQP from the different sub-themes will receive capstone training in systems level analysis, large scale economics and policy.

A Multidisciplinary Research Solution in Carbon Capture

Funded by NSERC